| 摘要 |
PURPOSE:To make accurate trouble diagnosis possible by opening/closing an EGR valve at the time of the decelerating operation of an engine, measuring the change of an intake amount which is generated at the time of opening/closing, and judging the presence of the trouble of an EGR device by the measured result. CONSTITUTION:During the running of a vehicle, when a throttle valve 10 is closed and an idle switch 12 is made to be ON while the engine speed which can be calculated from the power of a crank angle sensor 19 is reduced, the engine is judged to be in the decelerating operational state in an ECU 4 so that a trouble diagnostic circuit is made to start. Then, when a specified period passes in the decelerating operational state, an intake amount V1 at the time when an EGR valve 3 is fully closed is measured by an air flow sensor 6 and memoried. Next, the EGR valve 3 is fully opened for a specified period, and an intake amount V2 after a specified period is measured. Difference between said measured flow amounts is calculated and compared with judging value. When difference between the measured flow amounts is below the judge value, the EGR valve 3 is judged to be in the state of trouble so that an alarm lamp is lighted. |
